Apparatus for coupling rupture disc and perforated casing

ABSTRACT

An apparatus for coupling a rupture disc and a perforated casing is disclosed and pertains to the field of petroleum and gas field development tools. The apparatus includes a coupling body. Axially extended swells are provided at intervals in a circumferential direction on the coupling body. Several radial openings are provided on each swell. A nut is provided in each opening. A rupture disc is provided between one end of the nut and a bottom of the opening. A fixing cap is provided at the other end of the nut. A cavity with particular air pressure is formed by the fixing cap, the nut, and the rupture disc. An upper end of the fixing cap is coated with a self-dissolvable softening film. When the apparatus of the present invention is used to perform perforating or fracturing, structural force of a connected casing is not impaired.

TECHNICAL FIELD

The present invention pertains to the field of petroleum and gas field development tools, and specifically, to an apparatus for coupling a rupture disc and a perforated casing.

BACKGROUND

Fracturing is a main stimulation for petroleum and gas field exploration and development, and perforating is an important step before the fracturing. Currently, there are mainly two types of perforating operations: conventional perforating and hydraulic jet perforating. The conventional perforating operation is to start blasting and perforating after a perforating gun is run to a predetermined layer in a well, so that a formation fluid flows into the well. In this operation mode, construction costs and risks are both high; a professional construction team is required; the perforating gun and perforating charges need to be specially stored, transported, and maintained; after the perforating, a casing diameter tends to increase, and casing strength is reduced; and after the number of perforations is controlled, an implementation effect of limited entry cluster fracturing is poor, and there is also a great adverse impact on a petroleum and gas reservoir. The hydraulic jet perforating mainly uses a high flow nozzle to generate a perforation at a target layer by jetting, so that a formation fluid flows into a well. This operation causes much less damage to a petroleum and gas reservoir. However, this operation still requires that a dedicated tool should be first run into the well and pulled out of the well after completion of perforating. The construction procedure is complex, and costs are high. Moreover, a quantity of horizontal wells has increased quickly in recent years, but there is also great difficulty in using the conventional perforating modes to perform operations in horizontal wells.

SUMMARY

In view of disadvantages of the prior art, the present invention provides an apparatus for coupling a rupture disc and a perforated casing to achieve the following objectives: There is no need to run a dedicated perforating tool into a well, casing strength is not impaired, construction costs can be reduced, a construction period can be shortened, and perforating operation difficulty in a horizontal well can be reduced.

To achieve the objectives, the present invention uses the following technical solution:

An apparatus for coupling a rupture disc and a perforated casing includes a coupling body, where axially extended swells are provided at intervals in a circumferential direction on the coupling body, several radial openings are provided on each swell, a nut is provided in each opening, a rupture disc is provided between one end of the nut and a bottom of the opening, a fixing cap is provided at the other end of the nut, a cavity with particular air pressure is formed by the fixing cap, the nut, and the rupture disc, and an upper end of the fixing cap is coated with a self-dissolvable softening film.

Further, an interval between the adjacent swells is 90°.

Further, a quantity of the openings on each swell is 3 or 4.

Further, the air pressure in the cavity is standard atmospheric pressure.

Compared with the prior art, the present invention has the following beneficial effects:

The apparatus of the present invention and a connected casing are together run to a bottom of a well, and a well cementing operation is completed. There is no need to pull the apparatus and the casing out. During a perforating operation, it is only necessary to pierce an opening by using a high-pressure fluid and jet the fluid out of a perforation. Therefore, when this technology is used to perform perforating, there is no need to run a dedicated perforating tool into the well, a trip time can be saved, and a construction period can be shortened. For a perforating operation in a horizontal well, a conventional perforating tool is usually not capable of centering. This not only increases operation difficulty, but also affects perforation quality. In contrast, the apparatus is directly fitted onto a well wall, a non-centering problem does not occur, the process is simple, and therefore, perforating difficulty in the horizontal well is reduced. On the other hand, every time the conventional perforating tool is run to the bottom of the well, one staged perforating operation is completed. In the present invention, one casing string can be used to run a plurality of such apparatuses into the well, and therefore, a plurality of staged perforating operations can be completed in one trip, and efficiency is significantly improved. In addition, because the perforating operation is performed only at the opening of the apparatus, structural force and strength of the connected casing are not impaired.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an overall structure of an apparatus according to the present invention;

FIG. 2 is a schematic diagram of a cross-section of an apparatus according to the present invention;

FIG. 3 is a schematic diagram of connections between components in an opening; and

FIG. 4 is a schematic diagram of a connection between an apparatus and a casing according to the present invention.

In the drawings: 1. coupling body; 2. nut; 3. rupture disc. 4. fixing cap; 5. self-dissolvable softening film; 6. swell; 7. opening; 8. casing.

DESCRIPTION OF EMBODIMENTS

The following describes a structure and a principle of the present invention in detail with reference to accompanying drawings.

As shown in FIG. 1 and FIG. 2, an apparatus for coupling a rupture disc and a perforated casing includes a coupling body 1, where axially extended swells 6 are provided at intervals in a circumferential direction on the coupling body 1, several radial openings 7 are provided on each swell 6, a nut 2 is provided in each opening 7, a rupture disc 3 is provided between one end of the nut 2 and a bottom of the opening 7, a fixing cap 4 is provided at the other end of the nut 2, a cavity with standard atmospheric pressure is formed by the fixing cap 4, the nut 2, and the rupture disc 3 (referring to FIG. 3) together, and an upper end of the fixing cap 4 is coated with a self-dissolvable softening film 5.

An operating principle of the present invention is as follows: Before an operation, when the fixing cap 4 is mounted, the pressure in the cavity formed by the fixing cap 4, the nut 2, and the rupture disc 3 is the standard atmospheric pressure. Therefore, startup pressure of the rupture disc 3 can be accurately controlled, and there is no need to consider formation pressure comprehensively. The self-dissolvable softening film 5 applied to the upper end of the fixing cap 4 isolates each component in the opening 7 from well cement, and completely dissolves within a period of time by virtue of its self-dissolving characteristic, thereby preventing the opening 7 from being completely fixed by cement after well cementing.

During the operation, the apparatus of the present invention and a connected casing 8 (referring to FIG. 4) are together run to a bottom of a well, and a well cementing operation is completed. When perforating and production are required, a straddle tool or a dual-K344 tool is connected to each end of the apparatus of the present invention by using a conventional petroleum pipeline or a continuous petroleum pipeline, and then pressure of the petroleum pipeline is increased; when the pressure reaches the startup pressure (3000 psi to 4000 psi) of the rupture disc, the rupture disc 3 bursts, and further, the fixing cap 4 bursts, and then high-speed hydraulic washout is performed continuously; and approximately five minutes later, cement and rocks near the fixing cap and the opening are in a broken state and peeled off, and further, a perforation is formed. 

What is claimed is:
 1. An apparatus for coupling a rupture disc and a perforated casing, comprising a coupling body (1), wherein axially extended swells (6) are provided at intervals in a circumferential direction on the coupling body (1), several radial openings (7) are provided on each swell (6), a nut (2) is provided in each opening (7), a rupture disc (3) is provided between one end of the nut (2) and a bottom of the opening (7), a fixing cap (4) is provided at the other end of the nut (2), a cavity with particular air pressure is formed by the fixing cap (4), the nut (2), and the rupture disc (3), and an upper end of the fixing cap (4) is coated with a self-dissolvable softening film (5).
 2. The apparatus for coupling a rupture disc and a perforated casing according to claim 1, wherein an interval between the adjacent swells (6) is 90°.
 3. The apparatus for coupling a rupture disc and a perforated casing according to claim 1, wherein a quantity of the openings (7) on each swell (6) is 3 or
 4. 4. The apparatus for coupling a rupture disc and a perforated casing according to claim 1, wherein the air pressure in the cavity is standard atmospheric pressure. 